Description

This is my first ticket, apologies if this is known or I've missed something in my report.

With model A and model B, where model B has a fk to A:

A().b_set.all().only('pk')

Raises "FieldDoesNotExist: B has no field named 'pk'"

In my example I'm instantiating a new object for brevity. The behaviour is the same with a saved object.

I've attached a simple patch, however I couldn't get the testrunner working, so I couldn't write a full patch. Also, I expect this isn't the best method, but I don't know enough about the ORM to know of a better fix.